| Summary: | 碩士 === 國立中央大學 === 機械工程學系 === 107 === Nowadays, there have been a lot of methods to measure liquid’s density, viscosity and surface tension coefficient at room temperature. However, it become harder and the instrument is more expensive when measuring physical properties at high temperature. In addition, most of the present methods can only measure one or two physical properties at the same time. Recently, a method called Draining Vessel Method has been developed to simultaneously measure density, viscosity and surface tension coefficient. In the draining vessel, the drag force caused by viscosity and surface tension coefficient balances the driving force of gravity. We developed the algorithm by sensitivity analysis. The nonlinear regression was used to calculate the fluid properties of water and tin by minimizing the difference between the elevation heads gained from simulation and experiment.
The obtained results for water at 25 ℃ show the physical properties were measured with the percentage error of -1.71 % in density, -4.22 % in viscosity and 9.81 % in surface tension coefficient compared to the values quoted from literature. The results for 60 ℃ water show the percentage errors of -2.33 %, -3.92 % and 9.51% in density, viscosity and surface tension coefficient, respectively. The measured results for tin at 250 ℃ are -2.25 % in density, -0.18 % in viscosity and 7.86 % in surface tension coefficient. In order to increase the accuracy for measuring, it can decrease the size of the orifice to enhance the influence of surface tension coefficient. This study develops a method of measuring density, viscosity and surface tension coefficient simultaneously, and its feasibility is verified both with the cold and hot fluid fields.
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